Lindsay Lohan Drank, "Giggled" as She Tweeted Drug Confession

Lindsay Lohan certainly sounded contrite in her confessional Sept. 17 Tweet, in which she admitted to failing a drug test. ("I'm taking responsibility for my actions and am prepared to face the consequences," Lohan, 24, wrote.)

But a witness saw the star craft her statement that night on her Blackberry at Hollywood eatery Magnolia -- and tells the new Us Weekly that a flippant Lohan laughed and quaffed Jack and Cokes as she typed.

Lohan composed her missive as her assistant and a male pal coached her on how to make it "more personal," the witness recounts. "Her friend would say, 'No, use 'setback,' don't say 'mistake.' They'll say you make mistakes all the time!" The friend went on, "It's better to say you're responsible. Denying it will just get everyone mad per usual." Lohan's response: "She giggled" and had her assistant order her another Jack and Coke, the Magnolia spy tells Us.

Us Weekly also reports that mom Dina told guests at her Sept. 17 birthday party at Madeo's Restaurant in Roslyn Heights, NY, that her daughter - due in court Friday - would get off scot-free. "She said, 'Who cares if it's true? Our new team is like a machine. They'll squash this.'"